Multiferroic materials have caught significant attention in the last decade because of its interesting properties and intriguing coupling between different order parameters. SmFeO3 was predicted as a new type of room-temperature multiferroic system ever since 2012. It exhibits antiferromagnetism and significant magnetization below TN ∼ 670 K. However, the existence of ferroelectricity of SmFeO3 single crystal is still under debate. In this work, we process the growth of SmFeO3 thin films on various single crystalline substrates, which has rarely been done hitherto. An elegant combination of multiple characterizations has been conducted to identify the ferroic natures of SmFeO3 thin films. Atomic force microscopy is used to check the thin film surface, certifying the layer-by-layer growth nature. The interfacial strains are calculated by using high resolution XRD. X-ray absorption spectroscopy is used to determine the electronic structures. Piezoresponse force microscopy has clearly identified the ferroelectricity of SmFeO3 grown on NdGaO3 substrate. Furthermore, we processed first principle calculation to determine the origin of the ferroelectricity observed in the thin films. The information pileup reveals a new room temperature single-phase multiferroic system.